This prospective, randomized phase II trial is designed to evaluate whether low-dose short-course radiotherapy differs from common-dose short-course radiotherapy in terms of efficacy when both regimens are sequentially combined with CAPOX, a PD-1 monoclonal antibody, and interleukin-2 (IL-2) in patients with locally advanced rectal cancer. The study is based on findings from our previous single-center, single-arm PRIDE01 study, in which neoadjuvant short-course radiotherapy followed by systemic chemoimmunotherapy and IL-2 demonstrated encouraging antitumor activity relative to historical short-course radiotherapy-based approaches. The current trial aims to provide more robust clinical evidence regarding the potential role of low-dose radiotherapy combined with IL-2 as a sensitization strategy in multimodal neoadjuvant therapy. By comparing complete response rates between the two radiotherapy dose levels, this study may help define an optimized neoadjuvant approach and support future organ-preservation strategies for patients with locally advanced rectal cancer.